How do you iterate over records using a cursor in IndexedDB?

Question

Rana Sunny · Answer

You can iterate over records in IndexedDB using a cursor, which allows you to go through each record one-by-one—great for large datasets or conditional processing.
Basic Syntax for Cursor Iteration
const request = indexedDB.open("MyDB", 1);
request.onsuccess = function (event) {
    const db = event.target.result;
    const transaction = db.transaction("users", "readonly");
    const store = transaction.objectStore("users");
    const cursorRequest = store.openCursor(); // You can pass key ranges too
    cursorRequest.onsuccess = function (event) {
        const cursor = event.target.result;
        if (cursor) {
            console.log("Key:", cursor.key, "Value:", cursor.value);
            // Move to next record
            cursor.continue();
        } else {
            console.log("No more entries.");
        }
    };
    cursorRequest.onerror = function (event) {
        console.error("Cursor error:", event.target.error);
    };
};
You Can Use Cursor With:
Type
Example
Whole object store
store.openCursor()
Index
index.openCursor()
Range query
store.openCursor(IDBKeyRange.bound(1, 100))
Direction
store.openCursor(null, 'prev')
Example: Read All Users Where Age andgt; 30
store.openCursor().onsuccess = function (event) {
    const cursor = event.target.result;
    if (cursor) {
        const user = cursor.value;
        if (user.age andgt; 30) {
            console.log("User over 30:", user);
        }
        cursor.continue();
    }
};
Cursor Methods
Method
Purpose
cursor.continue()
Move to next record (default)
cursor.advance(n)
Skip n records
cursor.update(value)
Update current record
cursor.delete()
Delete current record
Update Record During Iteration
if (cursor.value.active === false) {
    const updated = { ...cursor.value, active: true };
    cursor.update(updated);
}
Summary
Feature
Supported in Cursor
Loop through all
Yes
Filter conditionally
Yes (custom JS logic)
Read/write/delete
Yes (in readwrite mode)
Performance
Efficient for large data

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How do you iterate over records using a cursor in IndexedDB?

Rana Sunny

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1 Answers

Basic Syntax for Cursor Iteration

You Can Use Cursor With:

Example: Read All Users Where Age > 30

Cursor Methods

Update Record During Iteration

Summary

Liked By

Type	Example
Whole object store	`store.openCursor()`
Index	`index.openCursor()`
Range query	`store.openCursor(IDBKeyRange.bound(1, 100))`
Direction	`store.openCursor(null, 'prev')`

Method	Purpose
`cursor.continue()`	Move to next record (default)
`cursor.advance(n)`	Skip `n` records
`cursor.update(value)`	Update current record
`cursor.delete()`	Delete current record

Feature	Supported in Cursor
Loop through all	Yes
Filter conditionally	Yes (custom JS logic)
Read/write/delete	Yes (in readwrite mode)
Performance	Efficient for large data